Extension of the typing in a general-primer-PCR reverse-line-blotting system to detect all 25 cutaneous beta human papillomaviruses

β-Papillomaviruses (PV) seem to be involved in the pathogenesis of cutaneous squamous cell carcinoma and its early stage actinic keratosis. In this study, typing was extended of a previously described consensus primer-mediated β- and γ-cutaneous HPV PCR method followed by reverse-line-blotting (BGC-PCR/RLB) to detect all 25 known β-PV and to examine their prevalence in actinic keratosis. The typing format of the BGC-PCR assay was extended by adding hybridization probes of six β-PV (HPV 75, 76, 80, 92, 93, and 96) to the RLB system. Subsequently, tumor and normal skin tissues were collected from 75 patients with actinic keratosis, allowing typing for a total of 25 β- and 5 γ-types. The analytical sensitivity was between 10 copies (HPV 75, 80, 92, 93, and 96) and 100 copies (HPV 76). Except for that of HPV 76, none of the added probes showed any cross-hybridization with other β-HPV. HPV DNA was detected in 45% of actinic keratosis and in 33% of normal skin by BGC-PCR, and at least one of the six added β-types was present in 19% of actinic keratoses and in 13% of normal skin. Six β-HPV types were added successfully to the typing format of the BGC-PCR/RLB system. The potential role of these types in the development of non-melanoma skin cancer awaits further studies.